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| United States Patent |
5,615,559
|
|
Kress
, et al.
|
April 1, 1997
|
Method and apparatus for recirculating product in a refrigeration system
Abstract
A freezing system for processing frozen edible product includes a freezing
section, an inlet section, a product discharge section, and a
recirculation section that selectively recycles processed product through
at least a portion of the outlet section back to the freezing section.
| Inventors:
|
Kress; John E. (Waterloo, WI);
Griffin; James W. (Fort Atkinson, WI)
|
| Assignee:
|
APV Crepaco Inc. (Rosemont, IL)
|
| Appl. No.:
|
396553 |
| Filed:
|
March 1, 1995 |
| Current U.S. Class: |
62/68; 62/136; 62/348 |
| Intern'l Class: |
A23G 009/00 |
| Field of Search: |
62/342,348,68,136
|
References Cited
U.S. Patent Documents
| 1742171 | Dec., 1929 | Vogt.
| |
| 1934283 | Nov., 1933 | Thompson.
| |
| 2263794 | Nov., 1941 | Wyen.
| |
| 2594442 | Apr., 1952 | Irwin.
| |
| 2784565 | Mar., 1957 | Stalkup | 62/348.
|
| 2896421 | Jul., 1959 | Rader | 62/348.
|
| 2975617 | Mar., 1961 | Wakeman.
| |
| 3037748 | Jun., 1962 | Wakeman.
| |
| 3214146 | Oct., 1965 | Wakeman et al.
| |
| 3829242 | Aug., 1974 | Duke et al.
| |
| 4129389 | Dec., 1978 | Wakeman et al.
| |
| 4793151 | Dec., 1988 | Masel et al.
| |
| 4850205 | Jul., 1989 | Mills.
| |
| 5016446 | May., 1991 | Fiedler.
| |
| 5024066 | Jun., 1991 | Goavec.
| |
| 5074125 | Dec., 1991 | Schifferly.
| |
| 5158506 | Oct., 1992 | Kusano et al.
| |
| 5201861 | Apr., 1993 | Menzel.
| |
| 5277037 | Jan., 1994 | Gram.
| |
| 5292030 | Mar., 1994 | Kateman et al.
| |
Primary Examiner: Tapolcai; William E.
Attorney, Agent or Firm: Leydig, Voit & Mayer, Ltd.
Claims
What is claimed is:
1. A system for processing frozen product comprising:
a freezing section disposed to receive unprocessed product at an inlet and
to supply processed product at an outlet;
an inlet section connected with the freezing section inlet operable to
supply a selected amount of unprocessed product to the freezing section
inlet;
an outlet section coupled between the freezing section outlet and a
downstream location, the outlet section including means for withdrawing
processed product from the freezing section and passing the processed
product to the downstream location;
a recirculation section coupled with the outlet section and the freezing
section inlet, the recirculation section including a diverter valve
operable, upon receipt of a first control signal, in a first position to
permit processed product to exit the outlet section and operable, upon
receipt of a second control signal, in a second position to supply
processed product through at least a portion of the outlet section,
through the recirculation section and to the freezing section inlet in
order to reduce the temperature of the portion of the outlet section; and
a control circuit including sensing means for sensing selected parameters
of the product and providing a sensing signal for selectively providing
the first and second control signals to the diverter valve in response to
the sensing signal.
2. The invention as in claim 1 wherein the inlet section comprises:
a product mix supply;
a mix pump coupled with the product mix supply and the control circuit for
controlling the pressure developed in the freezing section upon receipt of
a third control signal from the control circuit.
3. The invention as in claim 2 wherein the mix pump is a positive
displacement pump.
4. The invention as in claim 3 wherein the outlet section further comprises
a product discharge pump disposed in close relation to the freezing
section outlet and coupled with the control circuit operating at a
variable speed to control the flow of product through the freezing section
upon receipt of a fourth control signal from the control circuit.
5. The invention as in claim 4 wherein the mix pump is a centrifugal pump
and wherein the inlet section further comprises a mix flow meter coupled
with the mix pump disposed to monitor the amount of product provided by
the mix pump.
6. The invention as in claim 2 wherein the mixed pump is a centrifugal pump
and wherein the inlet section further comprises a mix for meter coupled
with the mix pump disposed to monitor the amount of product provided by
the mix pump.
7. The invention as in claim 1 wherein the freezing section comprises a
freezing cylinder, a dasher disposed in the freezing cylinder, and a drive
unit operable to rotate the dasher.
8. The invention as in claim 7 wherein the sensing means is coupled with
the drive unit and is disposed to provide a sensing signal when the load
on the drive unit exceeds a selected value.
9. The invention as in claim 8 wherein the control circuit includes an
electronic controller coupled with the sensing means.
10. The invention as in claim 8 wherein the sensing means further includes
a temperature sensor disposed in the freezing section providing a signal
indicative of freezing cylinder temperature.
11. The invention as in claim 1 wherein the sensing means includes a
temperature sensor disposed in the freezing section providing a signal
indicative of freezing cylinder temperature.
12. The invention as in claim 1 wherein the sensing means includes a
transducer disposed in the inlet section providing signals indicative of
the pressure applied by the unprocessed product in the inlet section.
13. The invention as in claim 9 wherein the inlet section includes a
preaerator disposed in the inlet section for mixing a selected amount of
air with the unprocessed product.
14. The invention as in claim 13 further comprising an air mass flow
controller coupled with the electronic controller and the preaerator
disposed to provide flow control signals to the preaerator.
15. A method for initiating a start-up operation in a system for processing
frozen product, the system including a freezing cylinder with an inlet and
an outlet, an inlet section supplying unprocessed product to the freezing
cylinder inlet, an outlet section receiving processed product from the
freezing cylinder, a recirculation section selectively coupled with the
outlet section and the freezing cylinder inlet, and a sensing and control
circuit providing control signals to the recirculation section, the method
including the steps of:
supplying unprocessed product from the inlet section to the freezing
cylinder inlet,
processing the product in the freezing cylinder,
passing the processed product from the freezing cylinder through the outlet
section,
sensing characteristics of the processed product with the sensing and
control circuit,
providing first control signals to the recirculation section for
selectively coupling the recirculation section with the outlet section and
the freezing cylinder inlet,
recirculating the processed product from the outlet section to the freezing
cylinder inlet at least for a selected period of time until the
temperature of the outlet section is reduced to a desired level,
providing second control signals to the recirculation section for
decoupling the recirculation section between the outlet section and the
freezing cylinder inlet, and
thereafter passing the processed product from the freezing cylinder through
the outlet section and to a downstream location.
16. A method for operating a system for processing frozen product including
a freezing cylinder with an inlet and an outlet, an inlet section
supplying unprocessed product to the freezing cylinder inlet, an outlet
section receiving processed product from the freezing cylinder, a
recirculation section selectively coupling the outlet section and the
freezing cylinder inlet, and control means for providing control signals
to the recirculation section, the method including the steps of:
supplying unprocessed product from the inlet section to the freezing
cylinder inlet,
processing the product in the freezing cylinder,
passing the processed product from the freezing cylinder through the outlet
section,
sensing the viscosity of the processed product with the control means,
providing first control signals to the recirculation section for
selectively coupling the outlet section with the freezing cylinder inlet,
recirculating the processed product from the outlet section to the freezing
cylinder inlet,
determining when the viscosity of the processed product exceeds a threshold
value, and
providing second control signals to the recirculation section for
decoupling the outlet section and the freezing cylinder inlet.
Description
FIELD OF THE INVENTION
This invention relates to apparatus and methods used in the continuous
production of edible product in refrigeration systems, and more
particularly, to methods and apparatus for recirculating processed frozen
product through outlet sections of the apparatus and reprocessing the
product during selected operations of the system.
BACKGROUND OF THE INVENTION
Conventional refrigeration systems used in the production of frozen
desserts and the like typically include a freezing cylinder that receives
unfrozen product mix from an inlet section and provides processed product
through an outlet section to a filler. In order to process the product
mix, the freezing cylinder is initially filled with unfrozen mix. The
refrigeration system surrounding the freezing cylinder is started. When
the freezing cylinder is filled, a dasher assembly in the freezing
cylinder is started so that blades attached to the dasher assembly scrape
the freezing cylinder wall to introduce ice crystals formed on the
cylinder wall with the product mix.
The viscosity of the product mix increases as its temperature decreases and
ice crystals are scraped from the freezing cylinder wall. The increased
viscosity is detected by monitoring the load on the dasher motor. When the
dasher motor-load rises to a predetermined level, forward flow of the
dessert mix begins. In particular, dessert mix and air is supplied under
pressure into the freezing cylinder. At the same time, frozen dessert from
the freezing cylinder exits to the outlet section and then to processing
equipment downstream of the freezing cylinder.
One of the problems associated with known refrigeration systems occurs
during a start-up operation of the system or at other instances where the
temperature of product lines downstream from the freezing is too high.
Otherwise, the viscosity and other characteristics of the processed
product is unacceptable for consumption. Accordingly, conventional wisdom
dictates that processed frozen dessert must initially be diverted to
nonproductive containers when forward flow of product commences until the
product lines are sufficiently cooled and product consistency is
acceptable to the operator. Thus, a substantial amount of product must be
diverted to a rework station due to the improper temperature of the
product lines. Inasmuch as various separate processing steps are required
for reconditioning the product prior to refreezing, in many instances the
product is simply discarded.
In addition, the frozen dessert is either diverted for reconditioning or is
destroyed when forward flow of the system is interrupted and then
restarted. This may be necessitated, for example, when intervention is
required for correcting problems with subsequent packaging stations or
with other equipment downstream from the freezing system. In some
instances, the product line must be shut down completely and restarted,
again resulting in unacceptable loss of product.
SUMMARY OF THE INVENTION
Accordingly, known systems now result in inefficiencies in production. It
is therefore an object of the present invention to overcome the
deficiencies of the prior art.
It is another object of the present invention to provide minimal product
loss in a refrigeration system.
It is an additional object of the present invention to substantially reduce
the amount rework of processed product in a refrigeration system.
The present invention provides these and other additional objects and
advantages with a freezing system that includes a freezing section having
a freezing section inlet and an outlet that processes product mix, an
inlet section coupled with the freezing section inlet, an outlet or
discharge section coupled with the freezing section outlet and a
recirculation section. The recirculation section is coupled with the
outlet section and the freezing section inlet and, when operating in a
selected mode such as a startup mode, recycles processed product after it
has been drawn through the outlet section back to the freezing section
inlet. At other times, the inlet section provides product mix to the
freezing section which is processed by the freezing section. The processed
product is then supplied via the outlet section to downstream locations.
During the recirculation mode, approximately 100 percent of the product mix
may be recirculated and reprocessed by the freezing section of the system.
Inasmuch as operating parameters of the freezing section may be
controlled, the product density and viscosity of the product mix may be
controlled when in the recirculation mode. In this way, the freezing
section and components in the outlet section are filled with food product
which is recirculated until a desired temperature is attained in the
outlet section of the system. In addition, processed product may be
recirculated from the outlet section back to the freezing section inlet in
other operating conditions, such as, for example, when downstream
packaging equipment is rendered inoperative. In this way, significant
amounts of wasted ice-cream are eliminated.
In a preferred embodiment, the inlet section of the system includes a
product mix pump that supplies product mix to the freezing section inlet
so that a desired pressure is maintained in the freezing section. The
outlet section likewise includes a product discharge pump that controls
product flow through the freezing cylinder. The product mix pump may be
implemented as a low cost centrifugal-type pump when the product discharge
pump is located in close relation to the freezing section outlet.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram representation of a refrigeration system for
processing frozen edible product according to the present invention.
FIG. 2 is an electrical block diagram representation of various components
in the system shown in FIG. 1.
FIG. 3 is a logical flow diagram for operation of a refrigeration system in
a FILL mode according to the present invention.
FIG. 4 depicts a logical flow diagram for operation of a refrigeration
system in a PROCESS or FREEZE mode.
FIG. 5 is a logical flow diagram for operation of a refrigeration system in
a HOLD mode.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Generally, the present invention relates to a refrigeration system for
processing frozen edible product that includes a freezing section, an
inlet section, an outlet or product discharge section, and a recirculation
section. The recirculation section selectively recycles processed product
by passing the product through at least a portion of the outlet section
and returning the product back to the freezing section for reprocessing.
This arrangement enables cooling of the outlet section components while
recycling the processed product, particularly during startup of the system
or at another desired time, to avoid waste of processed product. In this
way, the need for reworking the product is eliminated. Thereafter,
processed product may be discharged to further stations.
The system is intended for particular use in connection with processing
frozen or semi-frozen dessert products such as ice-cream, or other frozen
dairy products which are provided as a product mixture and typically
aerated to achieve a desired consistency when processed. However, the
system may be utilized in other applications where various components of a
refrigeration system must be brought to a selected temperature prior to
operation of the system with appropriate modification. Accordingly, the
term "frozen product" is used in the broadest sense herein and refers to
any product that is processed by refrigeration.
FIG. 1 is a block diagram of a refrigeration system 10 having a
recirculation arrangement 12 according to the present invention. The
refrigeration system 10 includes a freezing cylinder 14 surrounded by
refrigeration apparatus 16 as will be generally known to those skilled in
the art. The freezing cylinder 14 includes a freezing cylinder inlet 18
that receives unprocessed product mix from an inlet section 20. The
freezing cylinder 14 also includes a dasher element shown schematically as
element 22 disposed within the freezing cylinder.
In operation, the freezing cylinder is filled with product mix. The dasher
element 22 is then rotated by a dasher motor (denoted as numeral 24 in
FIG. 2) to stir the product mix contained in the freezing cylinder while
the product is cooled. The dasher element 22 also scrapes ice crystals
from the interior surface of the freezing cylinder so that the viscosity
of the product is increased as will be understood by those skilled in the
art. Processed frozen product is thereafter available via a freezing
cylinder outlet 26 at an outlet section 28. In this way, the freezing
cylinder processes the edible product.
The inlet section 20 includes a product mix tank 30 which supplies product
mix through a tank shutoff valve 32 to conduit denoted by a line 34. The
product mix is provided on line 34 to a mix pump 36 and thereafter to a
mix flow meter 38 via a line 40. The mix flow meter 38 may be implemented
as a mass flow meter which provides appropriated sensing signals (as
explained below) so that the flow of product mix may be closely monitored.
The product mix is thereafter provided to a preaerator 42 via conduit
denoted by a line 44. The preaerator 42 also receives a selected amount of
air which is metered thereto from an air input line 46. The preaerator
operates in a known fashion to mix the selected amount of air with the
product mix. The aerated product mix or overrun is provided via conduit
denoted by a line 48 to a pressure transducer 50 that senses the input
line pressure. The product mix is then applied through a T-type connection
52 via a line 54 and thereafter to the inlet 18 of the freezing cylinder.
In this way, the freezing cylinder pressure is controlled.
The discharge section 28 also includes conduit represented by a line 56
which receives exiting product provided the freezing cylinder outlet 26.
The frozen or processed product passes through conduit 56 under control of
an output or product discharge pump 58. The product discharge pump 58 is
preferably a positive displacement type pump that is operated in response
to a variable speed drive to control the product mix flow through the
freezing cylinder 14 and the discharge section. The processed product is
then supplied through conduit shown as an output line 60 to a three-way
divert valve 62. Alternatively, other similar valve systems may be used in
place of the three-way divert valve 62 such as, for example, two
single-seat valves.
The recirculation arrangement 12 includes the divert valve 62 which
selectively diverts the frozen product to a recirculation conduit 64. The
recirculation conduit 64, in turn, is coupled with the freezing cylinder
inlet 18 via the T-connection 52 at its other end. In this way, the
processed product may selectively be recycled back to the freezing
cylinder inlet 18 when desired such as, for example, during a startup
operation of the system. Alternatively, the divert valve 62 may be set to
supply the frozen product to further processing stations via conduit
represented by a line 66. By way of example, the frozen product may be
supplied to a filler processing station 68. Alternatively, other
ingredients may be added to the frozen product with an ingredient filler
prior to introduction to the filler station 68 as will be understood by
those skilled in the art. When an ingredient filler is utilized, the
recirculation arrangement is located upstream of the filler.
One of the advantages of the particular embodiment of the present invention
described herein is that the mix pump 36 may be implemented as a
centrifugal pump. This arrangement significantly reduces the overall cost
of the system. In this embodiment, the mix flow meter 38 is utilized to
monitor the flow of the product mix so that appropriate compensation may
be provided for any slippage due to the pressure differential between the
input and output of the mix pump 36. On the other hand, the product
discharge pump 58 is a positive displacement pump preferably located in
close proximity to the freezing cylinder outlet 26.
Alternatively, the mix pump 28 may also be implemented as a positive
displacement pump when greater precision in the operation of the system is
desired. This embodiment eliminates the necessity for the mix flow meter
30 in the input section since adequate information signals relating to
product mix flow pressure may be obtained from signals provided by the
positive displacement pump.
FIG. 2 is an electrical block diagram illustrating a preferred control
scheme for the freezing system 10. As shown therein, the freezing system
10 may operate under control of a electronic programmable logic controller
70. In operation, the electronic controller 70 receives dasher motor load,
freezing cylinder temperature, inlet section pressure, mix flow meter and
other information input signals as shown at the left of FIG. 2. The
electronic controller 70 operates in a logical fashion to provide a mix
pump control signal on a line 72, a tank shut-off valve control signal on
a line 74, a product mix flow meter control signal on a line 76, an air
mass flow control signal on a line 78, a freezing system control signal on
a line 80, a dasher motor control signal on a line 82, a product discharge
pump control signal on a line 84, and a recirculation divert valve control
signal on a line 86.
The signal on the line 74 to the tank shut-off valve enables product mix
flow from the mix tank supply. The signal on line 78 is provided in
response to the mix flow meter input information signals and pressure
input signals provided to the electronic controller 70 and controls an air
mass flow controller 90. The air mass flow controller provides via line 46
a desired air quantity to the pre-aerator so that overrun of the product
mix is controlled. Alternatively, where the mix pump is a positive
displacement pump, the controller 70 may process an output signal
indicative of overrun pressure from the mix pump to provide the control
signal on line 78.
The signals on lines 72 and 84 control operation of the product mix pump
and product discharge pump, respectively. The signal provided to the mix
pump on line 72 controls the freezing cylinder pressure. During
production, the controller 70 provides the signal on line 84 based on the
mix flow meter and inlet section pressure signals to control the mix flow
rate through the system. As noted above, the product discharge pump is
actuated by a variable speed drive to closely control mix flow rate. The
signal on line 80 controls operation of refrigeration apparatus 16
surrounding the freezing cylinder. Similarly, the signal on line 86
controls operation of the recirculation divert valve.
FIG. 3 is a logical flow diagram depicting the sequence of operation for a
FILL cycle of the freezing system 10. As shown therein, the system begins
at a block 100 and then advances to a decision block 102 and determines
whether appropriate input information is provided to the system to
initiate a FILL operation. If yes, the system advances to a block 104 and
provides appropriate control signals to actuate the mix pump. Preferably,
the mix pump is actuated so that it ramps up to a desired setpoint. This
is determined based on information signals received from the mix flow
meter. The product discharge pump is also initiated at a predetermined
speed.
The system then advances to a next block 106 where the tank shut-off valve
32 is opened. At the same time, air is metered into the input line and is
rationed in accordance with the output from the mix flow meter. The
preaerator is also actuated and the air mix flow controller 90 provides a
selected amount of air thereto based on information input signals provided
to the controller by the mix flow meter 38. The controller 70 also
provides appropriate control signals to set divert valve 62 to the
recirculation mode in order to recirculate product mix exiting the
freezing cylinder and outlet section of the system back to the freezing
section inlet. At the same time, any trapped air in the system is vented
through a vent valve (not shown) as will be understood by those skilled in
the art.
The system then determines at a decision block 108 whether a freezing
cylinder pressure threshold has been established by monitoring the input
information signal provided by the pressure transducer 50. When a
predetermined pressure is established, the system advances to a next block
110 and closes the vent valve. The system then advances to a decision
block 112 and determines whether the freezing cylinder pressure setpoint
has been obtained. Since the mix pump attempts to control the mix flow at
a predetermined flow rate and the system is closed, the mix pump stuffs
the system until the predetermined cylinder pressure is reached. Thus, if
at decision block 112 the desired cylinder pressure is not obtained, the
system advances to a decision block 114 and determines whether the same
operation input request is present. If no, the system advances to a
decision block 116 and determines whether the operator has requested a
system shutdown or hold operation. If yes, the system advances to a block
118 and initiates a shutdown operation. Typically, the shutdown operation
involves various cleaning and venting operations as will be understood by
those skilled in the art.
If, on the other hand at decision block 112, the system determines that the
freezing cylinder pressure setpoint has been reached, the system advances
to a next block 120 and closes the tank shut-off valve 32. The system also
begins a delay interval to deactuate the mix pump 36. In addition, the
appropriate control signals are provided to deactuate the air supplied on
line 46 and the preaerator 42. The divert valve 62 is maintained in the
divert position. The system then advances to a decision block 122 and
determines whether the mix pump delay interval has elapsed. If yes, the
mix pump is deactuated and the FILL cycle is completed.
FIG. 4 is a logical flow diagram showing the operation of FREEZE and RUN
cycles. As shown therein, the system first advances to a decision block
150 and determines whether the freezing cylinder is filled with product
mix.
If the system determines the FILL cycle has completed, the system then
advances to a block 152 where the electronic controller supplies
appropriate control signals to actuate the dasher motor 24 so that the
blades of the dasher element scrape the inside of the freezing cylinder
wall. The system also initiates the refrigeration apparatus surrounding
the freezing cylinder and the processing of the product mix within the
freezing cylinder is commenced.
The system then advances to a block 154 and maintains operation of the
product discharge pump at the selected speed. At the time, the divert
valve 62 is set to the recirculation mode to recycle the processed product
mix from the discharge or freezing section outlet through the product
lines of the outlet section and back to the freezing cylinder inlet.
The freezing cylinder processes the mix by increasing the viscosity thereof
in the freezing cylinder as more ice crystals are formed. In this regard,
the system then advances to a decision block 156 and determines whether
the dasher motor load has reached a threshold. If no, the system continues
to process the product mix. On the other hand, if the system determines
that the motor load is at the threshold, the system advances to a block
158 and initiates a viscosity control loop. The viscosity control loop
operates to control product viscosity by monitoring the dasher motor load.
In other words, increased product viscosity is detected by monitoring
increased motor load. When the dasher motor load increases to a selected
level, the electronic controller applies appropriate control signals to
the refrigeration system based on input information supplied by the dasher
motor. For example, when the system detects a decreased dasher motor load,
then the system responds by applying increased refrigeration. On the other
hand, if the motor load increases, less refrigeration is required. The
system is placed in a recirculation mode denoted by a next block 160 so
that the product exiting the freezing cylinder is recirculated through the
system to reduce the temperature of the downstream piping.
The freezing system operates in this configuration until all of the piping
and equipment downstream of the freezing cylinder are cooled to the
desired production temperature. The system then advances to a decision
block 162 and determines whether appropriate operator input has been
selected to initiate a RUN cycle. If yes, the system advances to a next
block 164. At block 164, the mix pump is actuated. At the same time, the
tank shut-off valve is opened. The system then advances to a next block
166 and initiates a mix flow loop timer. The system then advances to a
decision block 168 and determines whether the mix flow loop enable
interval has elapsed. In this regard, the mix flow loop is enabled after a
delay since there is typically a surge in the system on recharge.
Likewise, the tank shut-off valve may be opened after a delay to permit
the system to settle when initiating the forward flow mode. If at decision
block 168 the system determines that the interval has elapsed, the system
advances to a next block 178 and enables the mix flow control loop.
Forward flow is then accomplished by a temperature set point downstream or
operator intervention.
Thus, during the operation of a product run cycle, the input mix pump 36 is
actuated and controls the freezing cylinder pressure after the tank
shut-off valve 32 is open. The divert valve 62 is also set to a nondivert
mode and recirculation is discontinued. The output discharge pump 58
supplies processed product to the equipment downstream. In this regard,
the discharge pump controls product flow through the system with a
variable speed drive that receives control signals from the electronic
controller based on input signals received from the mix flow meter 38.
As described above, air is also rationed into the product mix input stream
in accordance with the signal supplied by the mix flow meter. Likewise,
the pre-aerator operates when mix flow is present. At the same time, the
refrigeration apparatus 16 operates under control of the dasher motor load
requirements.
The system may also operate under a HOLD cycle as shown in FIG. 5. This may
occur, for exampled when a problem is experienced downstream of the
freezing system 10. In order to initiate recirculation in this case, the
system begins at a block 200 and advances to a decision block 202. At
decision 202, the system determines whether the operator has input a HOLD
interrupt command. If yes, the system advances to a next block 204 to go
back into a recirculation mode. The system provides appropriate control
signals to deactuate the mix pump 36. The system also places the divert
valve to the divert position. The preaerator is also deactuated and the
tank shut-off valve is closed. Likewise, the cylinder pressure control
loop is disabled and airflow is turned off. The output discharge pump
still operates and the refrigeration system is controlled by the dasher
motor load requirements.
The system then advances to a decision block 206 and determines whether the
HOLD command is still being input by the operator. If no, the system
advances to a decision block 208 and determines whether a shutdown request
is input by the operator. If yes, the system advances to a block 210 and
initiates a shutdown procedure. If at decision block 208 the system
determines that a shutdown operation is not requested, the system returns
to decision block 206.
On the other hand, if at decision block 206, the system determines that the
HOLD input command is no longer requested, the system advances to a block
212 and actuates the mix pump 36. The system also moves the divert valve
62 to the nondivert position. In addition, the system enables the freezing
cylinder pressure loop and a time delay for enabling the product mix loop.
The system then advances to a decision block 214 and determines whether
the time delay for initiating the product mix loop has elapsed. If yes,
the system advances to a next block 216 and begins forward flow of
product, as described above in connection with FIG. 4.
When the system operates in the forward flow or RUN mode, recirculated
product is maintained in the recirculation line 64. Inasmuch as the
product in the recirculation line 64 is maintained at a relatively low
temperature, it may reside in the recirculation line until a next
recirculation operation is initiated. In typical food processing
operations, product in the recirculation line is brought to a temperature
of about 22.degree. F. so that, when periodic HOLD or RESTART cycles are
initiated, the product residing in the recirculation line does not warm to
a temperature above approximately 30.degree. F. Alternatively, a further
divert line may be connected between the recirculation line and the
freezing cylinder 14. In this way, the product residing in the
recirculation line may be displaced via air through the additional divert
line into the freezing cylinder.
Accordingly, a recirculation system meeting the aforestated objectives has
been described in terms of a number of preferred embodiments and the
features thereof. Those features which are deemed to be novel are set
forth with particularity in the appended claims. Such modifications and
alterations as would be apparent to those skilled in the art and familiar
with the teachings herein are also deemed to fall within the spirit and
scope of the present invention. For example, multiple freezing apparatus,
each with recirculation sections as described herein, may be disposed in
parallel relation for appropriate sizing of the production line.
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